Nitroglycerin-nitroglycol blasting composition

ABSTRACT

THIS INVENTION RELATES TO BLASTING COMPOSITIONS COMPRISING A BLASTING OIL, AND INORGANIC NITRATE AND CERTAIN DESENSITIZING AGENTS. THESE COMPOSITIONS ARE LESS DANGEROUS TO MANUFACTURE, LESS DANGEROUS TO HANDLE, AND LESS IMPACT SENSITIVE YET HAVING THE SAME HEAT OF EXPLOSION AND THE SAME BLASTING STRENGTH AS ORDINARY STRAIGHT ADYNAMITES.

y 13, 1971 r B. P. ENOKSSON 3,579,392

NITROGLYCERIN-NITROSLYCOL BLASTING COMPO S ITION Filed NOV. 27, 1968 2 Sheets-Sheet 1 H2 FIG. I.

B to Extrudclbility tdyn/cm 5 IO 2:) 30 4o 50 %Woter Content Of The Nitrocellulose Component FIG. 2.,

8 g D 5 K .2 E U! C 2 4 l- E \j g 2 f 2 X S 0 IO 20 3O 4O 5O Water Content Of The Nitrocellulose Component NITROGLYCERIN-NITROSLYCOL BLASIING COMPOSITION Filed Nov. 27, 1968 B. P. ENOKSSON May 18, 1971 2 Shoots-Sheet 2 FIG. 3.

80 9:. 0 ow. cocuwm 380 $5;

Grams Oxygen Per Grcim Explosive Composirion Legend -C0mpiete Propagation I- Deronorion Not Propagcied United States Patent 3,579,392 NITROGLYCERIN-NITROGLYCOL BLASTING COMPOSITION Bertil Petrus Enoksson, Gyttorp, Sweden, assignor to Nitro Nobel Aktiebolag, Gyttorp, Sweden Filed Nov. 27, 1968, Ser. No. 779,496 Claims priority, application Sweden, Nov. 27, 1967, 16,275/ 67 Int. Cl. C06b 1/04 US. Cl. 149-7 9 Claims ABSTRACT OF THE DISCLOSURE This invention relates to blasting compositions comprising a blasting oil, an inorganic nitrate and certain desensitizing agents. These compositions are less dangerous to manufacture, less dangerous to handle, and less impact sensitive yet have the same heat of explosion and the same blasting strength as ordinary straight dynamites.

Gelatin dynamite is manufactured by uniformly mixing the ingredients in a mixing and kneading machine to a suitable plasticity. Nitrocellulose is usually first added to a nitroglycerin-nitroglycol mixture to form a gelatin. Thereafter oxygen supplying salts (such as ammonium nitrate and sodium nitrate) and combustible components (such as wood meal and sulphur) are added.

The nitroglycerin-nitroglycol mixture as well as nitrocellulose are sensitive high explosive components which must be handled with great caution. In order to make the manufacture of blasting explosive compositions as safe as possible my concept is to introduce and handle these sensitive components in a desensitized form, i.e. by adding a desensitizing agent to reduce the oxygen balance to a negative oxygen balance or by adding it in combination with other components of the explosive composition.

THE INVENTION BROADLY The present invention generally pertains to a blasting composition of reduced impact sensitivity comprising:

(a) a liquid phase comprising (1) a nitroglycerin-nitroglycol mixture, and (2) a desensitizing agent which is soluble in the aforesaid mixture and which is present in an amount sufficient to lower the negative oxygen balance to about 20% or more, and dispersed therein (b) particles of an inorganic nitrate provided with a hydrophobic surface coating and possibly other common combustible components, stabilizers, and other additives.

Suitable desensitizers include non-explosive aromatic nitro-compounds or organic esters or others such as mononitrotoluene, dinitrotoluene or dibutylphthalate, or explosive organic nitro-compounds, such as trinitrotoluene. The desensitizing agent added to the sensitive nitroglycerin-nitroglycol mixture reduces the oxygen balance to a negative oxygen balance and the mixture can thus be handled more safely. In order to compensate for the reduced sensitivity of initiation of the blasting composition the ammonium nitrate components are provided with a surface active coating which reduces the wetting of the ammonium nitrate particles and hence air bubbles of suitable dimensions are retained on the salt crystals, improving the initiation sensitivity and at the same time giving a higher detonation transmission and better stability of detonation at low temperature. The surface coating of the nitrate component provides better water and moisture resistance which also improves propagation in small diameter charges.

The ammonium nitrate is rendered hydrophobic by means of surface treatment with a hydrophobic agent preferably an alkylamine having more than 6 carbon atoms in the alkyl group. Preferred alkylamines are those having 12 to 20 carbon atoms in the alkyl group such as dodecylamine, hexadecylamine, octadecylamine, oleylamine and stearylamine. Particularly suitable are mixtures of an alkylamine of the type mentioned and an alkyl ammonium salt of an aliphatic acid having at least 6 carbon atoms in the molecule. Such a mixture contains optimally 2-10 moles of alkylamine per mole of aliphatic acid. Both the alkylamine and the aliphatic acid should contain 12-20 carbon atoms in the molecule. As an example a molten mixture of stearylamine, technical octadecylamine or stearylpropylendiamine with technical stearic acid or palmitic acid is mentioned. The amount of surface active agent or surface active mixture is 0.0l1% of the weight of the inorganic nitrate preferably 0.0l0.1%.

The nitroglycerin-nitroglycol-nitrocellulose gelatin in the composition renders not only a suitable sensitiveness of initiation and a detonation stability but also protects the composition against water. Using heavily desensitized nitroglycerin-nitroglycol mixtures it is difficult to get a sufiiciently high content of gelatin and at the same time to have oxygen balance. This difficulty can be overcome by using trinitrotoluene as one part of the desensitizing addition. Trinitrotoluene is partly dissolved in the nitroglycerin-nitroglycol mixture and complete dissolving is attained after storing for some time and an excellent protection against water is achieved.

In determining the degree of desensitizing of the nitroglycerin-nitroglycol mixture it is important to decide the minimum cross-sectional area of a blasting composition column required for complete detonation propagation. As to nitroglycerin the situation is complicated as there exist two detonation velocities. To be quite sure it is necessary to consider the lowest detonation velocity which is propagated in a small dimension column. As low detonation velocities as about 1000 meters per second have been recorded.

Dry nitrocellulose is easily inflammable and burns violently. Moist nitrocellulose is much safer to handle. According to the present invention nitrocellulose can be included in the explosive in wet condition, containing 1S35% of water. Often the nitroglycerin-nitroglycol mixture is also dried in order to reduce the water content and at least the mixture is allowed to stand for separation of the emulgated water. Another advantage of the invention is that a moist nitroglycerin-nitroglycol mixture may be used in the composition thus eliminating storing and handling of the dried explosive mixture in the factory.

Previously it was not possible to improve the safety by employing moist components in the compositions of this type because the plasticity of the composition varies considerably depending on the Water content. Moreover the gelatin formed by adding moist nitrocellulose was not uniform and lumps were formed. The finished explosive composition was very difficult to initiate in cold conditions and upon storage.

The invention also relates to the manufacture of explosive compositions having the desired properties based on a nitroglycerin-nitroglycol mixture desensitized with at least 20% of desensitizing agent and 0*.31.0% of water and a nitrocellulose containing not less than 15% of water. In order to be able to cope with the problems caused by the water content the ammonium nitrate has been provided with a hydrophobic surface coating. Good results have been achieved when applying a coating consisting of a mixture of stearylamine and stearylammoniumstearate. By means of this coating the initiation of the explosive could be kept high and constant even at variations of the water concentration amounting to 1%. The

extrudability' of the composition has proved to be inde pendent on the water content of the composition over a still larger range. By combining a desensitized nitroglycerin-nitroglycol mixture, moist nitrocellulose and inorganic nitrate rendered hydrophobic, it was possible to carry out the manufacture safer and to have an explosive safer to handle compared to the conventional dynamite and still maintaining equally good initiation ability and strength even at a lower content of explosive mixture and a higher content of inorganic nitrates. The blasting composition may comprise one or several of the following components wood, meal, sulphur, pigments, stabilizers, and combustible metal powder such as aluminum.

The following examples illustrate specific embodiments of the invention.

EXAMPLE 1 Ten percent by weight of diethyleneglycol-monoethylether as a desensitizer was dissolved in a blasting mixture containing 60 parts by weight of nitroglycerin and 40 parts by weight of nitroglycol. The sensitivity to impact was determined with a falling weight of 2 kgs. While an untreated blasting mixture gave a 50% ignition probability at a height of fall of 100 mrn., a mixture having 10% addition of the above desensitizer required a height of fall of 500 mm. to cause the same ignition probability and failed to ignite at a height of fall of 100 mm. At a height of fall of 200 mm. the ignition probability for the mixture was 20%, and at a height of fall of 400 mm. the ignition probability was 40%. When desensitizing with 20% of diethyleneglycolmonoethylether no ignition occurred, not even at the highest height of fall of the apparatus, i.e. 600 mm. Both the untreated and the desensitized mixture included ammonium nitrate and wood meal for achieving oxygen-balanced explosives.

EXAMPLE 2 Liquid nitrotoluene having a nitrogen content of 16% was added as desensitizer to nitroglycerin. The sensitivity to impact of the homogeneous solution was determined by a falling weight of 2 kgs. Untreated nitroglycerin exploded in 50% of the cases at a height of fall of 100 mrn., but when desensitized by addition of 15-17% of the desensitizer no ignition occurred at a height of fall of the falling weight of 100 mm. and only 10% ignition was obtained at 200 mm. When adding 20% of the above desensitizer ignition occurred first at a height of fall of 500 mm. (10%) and when the desensitizer content was increased to 2530% no ignition occurred even at a height of fall of 600' mm.

Both (a) nitroglycerin and (b) desensitized nitroglycerine with 20% of desensitizer were converted to plastic compositions by adding 5% of synthetic silicon dioxide. In testing the desensitized nitroglycerin, ignition failed to occur even at a height of fall of 600 mm. while the non-desensitized composition ignited at a height of fall of 100 mm.

The desensitized nitroglycerin together with ammonium nitrate resulted in compositions having a somewhat lower detonation velocity and a lower detonation transmission from one cartridge to another cartridge compared to similar compositions containing non-desensitized nitro glycerin. However, the diiference was insignificant when blasting with the compositions in bore holes.

EXAMPLE 3 Friction tests were carried out by means of a steel shoe sweeping over a granite block at a temperature of 2030 C. The steel shoe was loaded with various weights. A nitroglycerin-nitroglycol mixture in the ratio 1:1 gave ignition in all ten tests carried out with a load of kgs. Nitroglycerin-nitroglycol mixtures containing 5, 10, 15, 20 and 25% dinitrotoluene exploded first at a load of 40, 90, 110 or more than 190 kgs. respectively.

4 EXAMPLE 4 40 kgs. of nitroglycerin-nitroglycol mixture in the ratio 1:1 were mixed with 14.3 kgs. nitrotoluene. To this solution 2.0 kgs. nitrocellulose comprising 25 of water were added and then 105 kgs. ammonium nitrate coated with 0.8% stearylamine and 1.5 kgs. wheat bran were mixed in a kneader. Extruding required a shear stress of 50 g./cm. The falling weight test was carried out with a 2 kgs. falling weight at a height of fall of 600 mm. not causing any ignition. The detonation velocity in a 25 mm. iron tube was 6320 m./sec. and the transmission of detonation for 25 mm. cartridges was 100 mm. at a temperature of 18 C. These properties remained unchanged after storage for one month.

EXAMPLE 5 A blasting composition as described in Example 4 was prepared but instead of wheat bran, wood meal was employed. The composition required at a shooting test with a bullet 4 times as much energy to cause ignition than corresponding compositions having the same gelatine content but the nitroglycerin-nitroglycol mixture being desensitized with only 7% of nitrotoluene.

EXAMPLE 6 When the nitroglycerin-nitroglycol mixture is highly desensitized the explosive becomes difficult or even impossible to be extruded in a standard press after storage for 3 days. As becomes evident from the table below, said disadvantage can be substantially overcome by re- I placing a minor portion of the ammonium nitrate by sodium nitrate. Explosives having the composition of 24.0% nitroglycerin-nitroglycol 40/70, 9.0% dinitrotoluene, 2.0% nitrocellulose containing 40% of water, 0.4% wood meal and 64% ammonium nitrate/sodium nitrate according to the table were prepared and the extrudability determined in a laboratory extruder. The extrudability expressed in g./cm. was:

NaNOa Time of storage:

hours 40 39 34 37 104 59 56 56 101 64 60 EXAMPLE 7 A plastic explosive was manufactured according to the following composition based on dry ingredients:

Percent Nitroglycerin-nitroglycol (40:60 ratio) 25.1 Dinitrotoluene' 7.0 Trinitrotoluene 1.8 Nitrocellulose of various moisture content l 1.3 Ammonium nitrate, coated 58.0 Sodium nitrate 6.0 Wood meal 0.7 Chalk and pigments 0.1

liquid components was elevated and the nitrate content was lowered according to the following composition:

Percent Nitroglycerin-nitroglycol (40:60 ratio) 28.1 Dinitrotoluene 8.0 Trinitrotoluene 3.8 Nitrocellulose of various moisture content 1.3 Ammonium nitrate, ground but untreated 52.6 Sodium nitrate 5.4 Wood meal 0.7 Chalk and pigments 0.1

The extrudability is shown in curve B of FIG. 1. When the water content in the nitrocellulose was less than 36% the explosive was hard and no figures could be measured in thelaboratory extruder. As becomes evident from FIG. 1 the consistency of this composition depends on the water content to a great extent. It is a considerable improvement to use surface coated ammonium nitrate in accordance with the first composition.

EXAMPLE 8 An explosive according to the first composition of Example 7 was manufactured from surface coated as well as uncoated ammonium nitrate. The transmission of detonation of the composition initiated by a pentylinitiator of 1 g. was determined. A composition containing ammonium nitrate coated with a hydrophobic surface detonated over a distance of 10 mm. no matter what the water content was in the included nitrocellulose over the whole tested range of from to 50% of water. The composition containing non-coated ammonium nitrate required a stronged initiator to cause any detonation transmission at all.

EXAMPLE 9 The transmission of detonation was determined in the same way as in Example 8 for an explosive of the following composition:

Percent Nitroglycerin-nitroglycol (40:60 ratio) 28.6 Dinitrotoluene 7.9 Nitrocellulose, various moisture content 1.5 Ammonium nitrate 60.8 Wood meal 1.4

The water content in the nitrocellulose varied from 0 to 55%.

As becomes evident from FIG. 2 low and greatly varying figures (curve C) were obtained for the detonation transmission when non-surface coated ammonium nitrate was used. Ammonium nitrate having a hydrophobic surface coating gives higher and, which is most important, more reproducable figures (curve D).

EXAMPLE 10 In nitroglycerin various amounts of dinitrotoluene and dibutylphthalate respectively were dissolved in order to obtain various degrees of negative oxygen balances. The solutions were filled in 300 mm. tubes of polyethylene and polyvinylchloride respectively of varying inner crosssectional areas and the tube ends were closed by means of corks. The tubes were initiated from one end by means of a No. 8 detonating cap. In FIG. 3 the figures for complete propagation and for detonation not propagated are plotted against the degree of negative oxygen balance of the solution. It is evident that when the negative oxygen balance reaches a higher balance than about the curve is rising and a possibility of getting satisfactory desensitizing is attained. A negative oxygen balance of 20% corresponds to an addition of 18% of dinitrotoluene dissolved in the nitroglycerin.

What is claimed is:

1. A blasting composition of reduced impact sensitivity comprising:

(a) a liquid phase comprising (1) a nitroglycerin-nitroglycol mixture, and (2) an organic desensitizing agent for said nitroglycerin-nitroglycol mixture in an amount sufiicient to lower the negative oxygen balance to about 20% or more, said organic desensitizing agent being dissolved in the nitroglycerin-nitroglycol mixture, and dispersed therein (b) an inorganic nitrate comprising ammonium nitrate provided with a surface coating of an alkyl amine having at least 6 carbons in the alkyl group.

2. A blasting composition according to claim 1 wherein the amount of the desensitizing agent is sufiicient to give a negative oxygen balance of about 20 30%.

3. A blasting composition according to claim 2 wherein the desensitizing agent is selected from the group consisting of a non-explosive organic ester and a non-explosive organic ether.

4. A blasting composition of reduced impact sensitivity comprising:

(a) a liquid phase comprising (1) a nitroglycerin-nitroglycol mixture, and (2) an organic desensitizing agent for said nitroglycerin-nitroglycol mixture dissolved in said mixture in an amount suificient to lower the negative oxygen balance to about 20% or more, said organic desensitizing agent being selected from the group consisting of mononitrotoluene, dinitrotulene, diethyleneglycol-monoethylether, trinitrotoluene, and dibutylphthalate and dispersed therein (b) an inorganic nitrate comprising ammonium nitrate provided with a surface coating of an alkyl amine having at least 6 carbons in the alkyl group.

5. A blasting composition according to claim 4 wherein the hydrophobic surface coating on the inorganic nitrate comprises an alkylamine having at least 6 carbon atoms in the alkyl group.

6. A blasting composition according toclaim 4 wherein the hydrophobic surface coating comprises (a) an alkylamine having at least 6 carbon atoms in the alkyl group and (b) an alkyl ammonium salt of an aliphatic acid having at least 6 carbons in the alkyl group and at least 6 carbons in the aliphatic acid.

7. A blasting composition according to claim 4 wherein the hydrophobic surface coating comprises (a) an alkylamine having between 12 and 20 carbon atoms in alkyl group and (b) an alkyl ammonium salt of an aliphatic acid having between 12 and 20 carbons in the alkyl group and between 12 and 20 carbon atoms in the aliphatic acid.

8. A blasting composition as claimed in claim 4 which additionally contains nitrocellulose containing at least 15% of Water.

9. A blasting composition according to claim 4 wherein the hydrophobic surface coating is selected from the group consisting of dodecylamine, hexadecylamine, octadecylam ne, oleylamine, stearylamine, stearylpropylene diamme, stearylammonium stearate, and mixtures thereof.

References Cited UNITED STATES PATENTS 3,039,903 6/ 1962 Enoksson l497 3,249,474 5 1966 Clay et a1. 1496 3,296,042 1/ 1967 Quadfleig et al 149-7 3,297,582 1/ 1967 Chrisp 149-6 3,346,429 10/1967 McMahon et al l497X 3,367,805 2/ 1968 Clay et al. 14 96 LELAND A. SEBASTIAN, Primary Examiner S. J. LECHERT, JR., Assistant Examiner US. 01. X.R. 

